The 2.6 m VST telescope is going to be installed at Cerro Paranal (Chile) as a powerful instrument for optical surveys. It is a joint project between the INAF - Osservatorio Astronomico di Capodimonte (OAC) and ESO. This paper deals with Telescope Control Software (TCS) technical aspects and software engineering design and development strategies

Brescia, M.

Mancini, D.

Marty, L.

Schipani, P.

Spirito, G.

English

Archivio della ricerca - Università degli studi di Napoli Federico II

Astronomical Data Analysis Software and Systems XIIIASP Conference Series, Vol. 314, 2004F. Ochsenbein, M. Allen, and D. Egret, eds.Software reverse engineering and development: the VSTTCS caseP. Schipani, M. Brescia, D. Mancini, L. Marty, G. SpiritoINAF - Osservatorio Astronomico di Capodimonte, Salita Moiariello 16,I-80131 Napoli, ItalyAbstract. The 2.6 m VST telescope is going to be installed at CerroParanal (Chile) as a powerful instrument for optical surveys. It is ajoint project between the INAF - Osservatorio Astronomico di Capodi-monte (OAC) and ESO. This paper deals with Telescope Control Software(TCS) technical aspects and software engineering design and developmentstrategies.1. IntroductionIn the framework of a Memorandum Of Understanding jointly signed by ESOand OAC, the OAC has been committed to design and realize the VST tele-scope, software included. Nevertheless after the installation and commissioningthe VST will be managed by ESO. Therefore in order to simplify the futuremaintenance of the software by ESO staff, it has been agreed to develop theVST software in the most “VLT-compliant” way. This constraint translatesinto pros and cons for OAC side, because many software utilities developed forVLT are available, but their migration to VST case requires a deep knowledgeof all details, usually known to the original software developers only. In thiscontext a reverse engineering approach, combined with the traditional softwaredevelopment for the VST specific subsystems, is the only solution.2. ArchitectureAs the VLT is a large project involving many staff people for many years, astrong standardization has been introduced by ESO in the software developmentand hardware platforms. The VST software is based on the same standard ar-chitecture: distributed workstations running HP-UX and VME-bus-based LocalControl Units (LCU) running the VxWorks real time multitasking operatingsystem, connected together via Local Area Networks. LCUs interface with fieldelectronics and electro-mechanics; the applications they run is a low level soft-ware, used to control and monitor the hardware devices, modularly distributedin processes and machines. The workstations coordinate LCUs and run thegraphical user interfaces and ”high level” application software; the workstationsoftware has time execution requirements less urgent than the LCU’s one, and isthe one the operators usually interface with. The basic ideas in the architectureare modularity and standardization. Each LCU is devoted to control a spe-697698 Schipani et al.Figure 1. VST Telescope Modelcific subsystem, so the hardware devices are driven independently by differentLCUs, using whenever possible the same VME boards and the same software.The programming languages on HP-UX platform are basically C++ for thecore control modules, and Tcl/Tk for graphical user interface development. TheLCU modules are developed in C. A key role in both workstation and LCUsoftware architecture is played by an On Line Data Base, which allows the on-line information sharing between modules, monitoring the status of the systemand of commands execution. Between the operating system and the applicationlayer there is another software layer developed by ESO for VLT and reused forVST, the VLT Common Software, providing a lot of utilities, tools and commonservices to the application programmer.Software reverse engineering and development 699Figure 2. VST Telescope Control Network Architecture3. Reverse EngineeringVLT software has been made available to Capodimonte staff, which was com-mitted to reuse it as much as possible. This has been certainly an advantagebecause many parts could be recycled for VST. But obviously many other partshave been rewritten (most of the LCU software) or partially modified. Modifyinga code that you do not know is often harder than rewriting it from scratch: thusa reverse engineering approach has been mandatory to let the old code run inthe different (for telescope hardware, no. of machines, telescope functionalities)VST environment, to understand its operation in terms of simple functionalityor in deeper details when needed, to change small or large parts preserving theinterlacing between the many applications, running on many different machines.Sometimes a lot of time has been necessary to change just a few lines of code.ESO assistance in this hard work solved only partially the problem, becausegenerally the help in this kind of work is fully effective only if persons work inthe same location and can be easily grouped around the same table (otherwise,even a trivial - for the original developer!- problem can take a long time to besolved).700 Schipani et al.4. Work descriptionUnlike other telescope projects of similar size, usually committed to large orga-nizations or consortia of many institutes, the whole VST design and realizationhas been committed to a small group (permanent research staff: 3 researchers+ 2 graduated level technicians) of a small observatory, involved also in otherparallel international programs. On software side, 2 permanent staff units havebeen available (1 has been deeply involved in other projects for the first years)+ 2 short term young contractors, who unfortunately have changed many timesalong the years, moving to better remunerated and permanent position jobs:this has caused continuous loss of know-how and restart of the training withnew contractors from scratch. It must be remarked that while in other work ar-eas the start-up period can be relatively short, obviously the training in this kindof work cannot produce short term results, because in order to be operationalit is necessary a good knowledge of computer science (e.g. Unix and Real-Timesystems, C++ and Tcl/Tk languages, VLT software environment - used onlyinside ESO projects), control engineering (e.g. feedback control theory, controlof industrial plants), very specialistic disciplines (e.g. active optics), daily tele-scope operation: no young engineer or astronomer with this skill is available atan affordable (for INAF-OAC) cost. It can be stated that VST telescope controlsoftware realization is an international level challenge faced with a low budgetand with an undersized staff in comparison with similar projects usually carriedout by larger staffs, generally spread within different research institutes.5. Status of workMost of the software is now (November, 2003) ready for tests with the telescope.Since this software interface with many external devices, it is foreseen a periodof intensive tests with real hardware in order to let the overall control system(software + electronics) working at its best.Acknowledgments. We are grateful to all those who have supported ourwork. S. Sandrock and R. Karban of ESO gave us precious suggestions in ourmigration from VLT to VST case.ReferencesBrescia, M., Mancini, D., Marty, L., Mazzola, G., Schipani, P., Spirito, G. 2002,Proc. SPIE, 4848, 553Schipani, P., Brescia, M., Mancini, D., Marty, L., Spirito, G. 2001, Proc. ofthe 8th International Conference on Accelerator and Large ExperimentalPhysics Control System, 579

Software reverse engineering and development: the VST TCS case

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Software reverse engineering and development: the VST TCS case

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